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The Second Genetic Code And Apparently A Third

Genes may or may not be switched on depending upon the addition of molecules called "methyl groups" to DNA. Now, a second kind of gene switch has been discovered on histones, a class of proteins.

Figuring out when methylation of histones takes place has far-reaching implications; acting as a second genetic code, histone methylation may determine genetic traits such as the susceptibility to disease.

Comment. So, beyond the first genetic code (the DNA) and the second genetic code (the recognized methyl groups), we now have some proteins (the histones) getting in on the act. And the show ain't over yet!